The principal investigator's previous relevant research has dealt with the pathogenesis of other autoimmune bullous diseases, namely epidermolysis bullosa acquisita and bullous lupus erythematosus. The focus has been on epitope mapping of type VII collagen, the target antigen in these diseases. In parallel, the focus of the primary sponsor's studies has been on the structure and function of desmoglein I (DG1) and three of its neighboring desmosomal components, desmocollins I and II and plakoglobin. Several members of the desmoglein family are the antigenic targets of adhesion-disrupting antibodies present in sera of patients with two other autoimmune bullous diseases: pemphigus foliaceus (PF) and pemphigus vulgaris (PV). The target antigens of PF and PV, desmoglein I and the closely related protein PVA, structurally form a distinct subset of the cadherins, a family of cell-cell adhesion and recognition molecules. A significant problem in this area of research, however, is that while DG1, the antigenic target of PF sera, is reported to be expressed throughout the epidermis, the blisters in PF occur in a very specific layer. Recent data have pointed to the potential for DG1 to comprise a number of different isoforms which may or may not be differentially expressed throughout the epidermis. The corresponding DNA sequences differ in the region encoding the part of DG1 close to the external face of the plasma membrane. The goal of this proposal, therefore, is to characterize the expression of several desmoglein isoforms and to determine their contribution towards normal cell adhesion and PF. The expression of the mRNA transcripts of these genes will be systematically explored using RNase protection, PCR and in situ hybridization techniques. Antibodies to bacterially expressed fusion proteins of these isoform-specific sequences will be raised and the distribution of these protein products in tissues examined by immunofluorescence and western blotting. The epitopes recognized by PF sera will be mapped either by examining their acantholytic activity on keratinocyte cultures following affinity purification on the fusion proteins or by the ability of cells to become susceptible to acantholysis after transfection with wild-type and chimeric forms of epidermal DG.